Nucleus Replacement Device and Method

ABSTRACT

A method of replacing a nucleus pulposus material wherein curable nucleus pulposus material is injected into a balloon in an intervertebral space

BACKGROUND OF THE INVENTION

The natural intervertebral disc contains a jelly-like nucleus pulposussurrounded by a fibrous annulus fibrosus. Under an axial load, thenucleus pulposus compresses and radially transfers that load to theannulus fibrosus. The laminated nature of the annulus fibrosus providesit with a high tensile strength and so allows it to expand radially inresponse to this transferred load.

In a healthy intervertebral disc, cells within the nucleus pulposusproduce an extracellular matrix (ECM) containing a high percentage ofproteoglycans. These proteoglycans contained sulfated functional groupsthat retain water, thereby providing the nucleus pulposus within itscushioning qualities. These nucleus pulposus cells may also secretesmall amounts of cytokines as well as matrix metalloproteinases(“MMPs”). These cytokines and MMPs help regulate the metabolism of thenucleus pulposus cells.

In some instances of disc degeneration disease (DDD), gradualdegeneration of the intervetebral disc is caused by mechanicalinstabilities in other portions of the spine. In these instances,increased loads and pressures on the nucleus pulposus cause the cells toemit larger than normal amounts of the above-mentioned cytokines. Inother instances of DDD, genetic factors, such as programmed cell death,or apoptosis can also cause the cells within the nucleus pulposus toemit toxic amounts of these cytokines and MMPs. In some instances, thepumping action of the disc may malfunction (due to, for example, adecrease in the proteoglycan concentration within the nucleus pulposus),thereby retarding the flow of nutrients into the disc as well as theflow of waste products out of the disc. This reduced capacity toeliminate waste may result in the accumulation of high levels of toxins.

As DDD progresses, the toxic levels of the cytokines present in thenucleus pulposus begin to degrade the extracellular matrix (inparticular, the MMPs (under mediation by the cytokines) begin cleavingthe water-retaining portions of the proteoglycans, thereby reducing itswater-retaining capabilities). This degradation leads to a less flexiblenucleus pulposus, and so changes the load pattern within the disc,thereby possibly causing delamination of the annulus fibrosus. Thesechanges cause more mechanical instability, thereby causing the cells toemit even more cytokines, thereby upregulating MMPs. As this destructivecascade continues and DDD further progresses, the disc begins to bulge(“a herniated disc”), and then ultimately ruptures, causing the nucleuspulposus to contact the spinal cord and produce pain.

Intervertebral disc degeneration causes a number of clinical problems,including sequelae related to reduced disc height and herniation. Inmany cases, a simple discectomy can effectively relieve pain, but intime results in further collapse of the disc space because theintervertebral disc can no longer resist body loads the same as ahealthy disc. Spine fusion procedures represent another state of the arttreatment for disc problems. Fusion generally involves the use ofinterbody fusion cages and spinal fixation systems to immobilize thefusion site.

In an effort to substantially maintain the patient's range of motion andto reduce tissue damage associated with surgical intervention, the arthas considered nucleus pulposus replacement and enhancement devices.Many of these devices are designed to fill at least a portion of thevoid left by removal of the nucleus pulposus portion of the disc andprovide joint flexibility and shock absorption. Some of the nucleuspulposus devices being evaluated are in situ cured (such as in situcured polyurethane contained within an outer bladder and in situ curedprotein polymers). Other devices under evaluation include relativelysolid hydrogels (such as hydrogel contained within a UHMWPE pillow andhydrogel balls).

Other intervertebral motion devices include devices having anarticulation interface and cushion-type devices.

Both the fusion and motion intradiscal implants require an accuratedetermination of the cleared disc space for the best performance,mechanical fit and material interdigitation of the device in order tominimize potential device movement and expulsion. Each of theabove-noted treatments involving an implant requires a removal of thenatural nucleus pulposus from the disc space. This procedure is called a“discectomy”.

The ability of a surgeon to accurately determine the position, size andshape of the cleared disc space during discectomy is currently limitedby many factors, including the procedure approach, access, location andthe size through the annular wall, as well as available intraoperativeimaging techniques. Improper location, size or shape of the cleared discspace following discectomy can greatly impact the size, placement andsecurement of intervertebral devices that are ultimately placed in thedisc space, as well as the biomechanical loading of the device and thephysiologic response to the device. For example, improper lateralplacement of a nucleus pulposus replacement device may cause migrationor expulsion of this implant, leading to continued height loss andirritation of neighboring tissues (including nerve roots), therebycreating additional pain or requiring re-operation.

When attempting to replace the nucleus of a damaged disc with a nucleusreplacement implant, the surgeon typically desires to attain a number ofrelated goals. First, the surgeon has a desire to adequately fill thedisc space following the removal of disc tissue, while avoidingunnecessary damage to the surrounding annulus fibrosus. There is afurther desire to intraoperatively visualize the space to be occupied bythe nucleus replacement so that the implant may be effectivelyimplanted. Next, there is a desire to avoid expulsation of the implanteddevice, which may occur either through the port through which theimplant is inserted or through natural annular fissures. Lastly, thereis a recognition that addition of radio-opaque agents to the implant mayhave a detrimental effect upon the performance properties of theimplant.

It is known in the medical field to deliver a curable material to asurgical site within an expandable device or membrane, such as aballoon. In some embodiments thereof, a curable cement is delivered to afractured vertebral body in order to strengthen the structure a regainits stability. In the area of nucleus pulposus replacement, it is knownto deliver the curable material through a catheter.

For example, US Published Patent Application Number 2005/0027358(“Suddaby”) discloses a nucleus replacement including a distendable sackor balloon which is inflated with a hardenable material and is detachedin situ when the injected material has hardened. Suddaby further teachesthat two nested balloons may be inserted, and then filled with materialswhich have different hardnesses when cured, to simulate a natural disc.

US Published Patent Application Number 2005/0245938 (“Kochan”) disclosesrepair of intervertebral discs with a catheter for inserting through acannula, the catheter having a distal end and a proximal end and a lumenextending longitudinally therethrough. An expandable balloon mayoptionally be detachably attached to the catheter near the distal end.The proximal end of the catheter is coupled to an injector that holds asupply of a thermoplastic elastomer material at a predetermined elevatedtemperature sufficiently high to maintain the thermoplastic elastomer ata liquid state. The device allows a thermoplastic elastomer material tobe injected into the intervertebral disc space or the articular jointspace as a replacement prosthetic for the disc's nucleus pulposus.

US Published Patent Application Number 2005/0251259 discloses a systemfor replacing a natural vertebral disc with a synthetic disc, saidsystem comprising an outer balloon adapted to be inserted into anintervertebral disc space, an inner balloon which can be inserted withinsaid first balloon, thus defining a chamber between said first balloonand said second balloon, a first hardenable material in liquid formadapted to be injected into said inner balloon, a second hardenablematerial in liquid form adapted to be injected into said chamber, saidfirst and second materials having different properties when hardened,and means for injecting said materials into said respective balloonswhile they are disposed within said intervertebral disc space, whereby asynthetic disc having inner and outer portions with different propertiescan be formed in said intervertebral space.

US Published Patent Application Number 2005/0209602 discloses anapparatus adapted to deliver a flowable biomaterial to an intervertebraldisc space, comprising: a reservoir containing the flowable biomaterialfluidly coupled to the intervertebral disc space; at least one sensoradapted to monitor at least one injection condition of the flowablebiomaterial; a controller programmed to; monitor the at least onesensor; control the flow of the flowable biomaterial into theintervertebral disc space in accordance with a first operatingparameter; controlling the flow of the flowable biomaterial inaccordance with a second operating parameter in response to one or moreof the injection conditions reaching a threshold level; and maintainingthe second operating parameter during at least a portion of the curingof the flowable biomaterial. incorporates sensors into its system.

US Published Patent Application Number 2003/0195628 discloses a methodfor repairing a damaged or diseased intervertebral disc, the methodcomprising the steps of: using minimally invasive techniques to removedamaged or diseased nucleus from the disc; providing a mold apparatuscomprising a balloon adapted to contain a biomaterial and a deliverycannula adapted to flowably connect a biomaterial source to the balloon;positioning the balloon in the intervertebral disc space using minimallyinvasive techniques; providing a biomaterial source comprising aplurality of components adapted to be mixed at the time of use toprovide a flowable biomaterial and initiate its cure; mixing thebiomaterial components; delivering the flowable biomaterial into theballoon using minimally invasive techniques to provide a distractionpressure to the intervertebral disc space; allowing the deliveredbiomaterial to cure to permit the cannula to be removed and to provide apermanent replacement for the nucleus; and applying mechanicaldistraction in combination with the pressurized injection of flowablebiomaterial to distract the intervertebral disc space.

US Published Patent Application Number 2005/0113923 teaches a method forimplanting a spinal disc nucleus pulposus implant, comprising: removingnucleus pulposus tissue from a spinal disc; and injecting abiocompatible material into an intradiscal space; wherein thebiocompatible material is injectable into the intradiscal space in afluid state below physiological temperatures, and is curable bytemperature alone via a reversible phase shift to form a gel atphysiological temperatures.

US Published Patent Application Number 2005/0065609 discloses a flexibleprosthetic cover shaped to form a replacement nucleus pulposus for anintervertebral disc and comprising an aperture for the introduction offilling material therein, and an elongate introducer member configuredto pass into the aperture, the cover having a strengthened portionsubstantially opposite the aperture for engaging the distal end of themember, the strengthened portion and the said distal end being arrangedto interlock, for facilitating orientation of the cover.

U.S. Pat. No. 5,888,220 (“Felt I”) discloses a nucleus pulposusreplacement device comprising an expandable bag into which in-situcurable polyurethane is injected. Felt further discloses that theplacement of the bag can be radiographically verified with the use of aC-arm. See also U.S. Pat. No. 6,248,131, US Published Patent ApplicationNos. US 2003/0220649 (“Felt II”) and US 2003/0195628. Felt II disclosessome embodiments in which the balloon has metallic wires or otherimageable means incorporated into it so that the balloon can be seenunder fluoroscopy. Felt discloses that potential imageable materialsinclude any metal, metal alloys, or ceramics that could be combined witha polymer, and that the imageable material can be in the form of wires,a mesh, or particles incorporated into the balloon or on its surface.

Felt does not disclose the use of a radiographic disc space trialballoon that is inflated to verify the size and geometry of the discspace.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a nucleusreplacement that can be delivered through a small portal to the spaceformerly occupied by the nucleus pulposus. It is another object of thepresent invention to provide a means by which the surgeon canintraoperatively determine the space being occupied by the nucleusreplacement.

The present invention relates to a nucleus pulposus replacement (NPR)delivered by a catheter and held within an expandable device ormembrane, such as a balloon. This configuration helps to reduce thepotential for expulsion, helps to distribute the stresses caused bydelivery of the nucleus replacement, and can provide the surgeon with ameans to determine the volume occupied by the nucleus replacement.

The balloon, which could be constructed from a resorbable material, isdelivered to the disc space via a catheter. This delivery method helpsto minimize the size of the defect made in the annulus fibrosus duringthe procedure. The catheter is inserted into the nuclear space followingthe removal of the native nucleus.

In a first embodiment, the balloon has two ports—an inlet port and anoutlet port. These ports can be connected to a pressure-measuringdevice. After the catheter is placed in the intervertebral space, theballoon is filled with a radio-opaque solution until the desired balloonvolume is attained. Following this, the nucleus replacement material isfed into the inlet port of the balloon, while the radiopaque agent isallowed to leave via the outlet port. A constant pressure is maintainedto ensure that the volume does not change. Once the balloon iscompletely filled, it (along with its ports) is allowed to sit until thenucleus material is fully cured. Once curing of the curable nucleusreplacement material is accomplished, the catheter, the inlet port andthe outlet port are removed, and the remaining annular defect can besealed.

In some preferred embodiments respecting sequential injection of fluids,the procedure is carried out with a single balloon having a single inletport and a single outlet port. After the balloon is inserted into thedisc space, the outlet port of the balloon is blocked. Next, the balloonis filled through the inlet port with a trial fluid, such as radiopaquesaline, and the sufficiency of the expanded balloon is then assessed. Ifthe assessment yields a satisfactory determination, then the surgeonsimultaneously opens the outlet port and fills the balloon with NPRimplant material. The radiopaque saline drains out the outlet port whileas the NPR implant material takes its place inside the balloon, therebyproducing a replacement implant.

Therefore, in accordance with the present invention, there is provided amethod of replacing a nucleus pulposus in an intervertebral disc,comprising the steps of:

-   -   a) removing the nucleus pulposus from the intervertebral disc to        create a space,    -   b) inserting into the space a balloon having an inlet port and        an outlet port,    -   c) conducting an amount of a first fluid comprising a radiopaque        agent through the inlet port and into the balloon to produce a        first pressure in the balloon,    -   d) conducting a second fluid comprising a curable nucleus        replacement material through the inlet port and into the balloon        to displace the first fluid through the outlet port.

In some embodiments having sequential injection of radiopaque andnucleus replacement materials, injection of the radiopaque materialsproduces a first pressure in the balloon, and the injection of thecurable nucleus replacement material is carried out at substantially thesame first pressure. In some embodiments thereof, the amount of theradiopaque fluid conducted into the balloon is measured prior toinjecting the curable nucleus replacement material. In some embodiments,the surgeon carries out fluoroscopic assessment of the balloon afterinjecting the radiopaque material and before injecting the curablenucleus replacement material. Preferably, the inlet and outlet ports areremoved from the balloon after curing is accomplished.

In addition, rather than filling the balloon with a radio-opaquesolution and risking interactions between the trial sizing fluid and thenucleus replacement materials, the balloon could be manufactured withradio-opaque properties. For example, the elastomer component of theballoon could be impregnated with a radiopaque material such as bariumsulfate or could be imprinted with tungsten ink. In these embodiments,the initial trialing fill of the radiopaque balloon could be a simplesolution such as water or saline.

Another method of controlling the size of the inflated balloon includesthe use of a volume control system. This embodiment can utilize syringesthat are actuated to eject controlled, discrete amounts of curablenucleus replacement material.

Therefore, in accordance with the present invention, there is provided amethod of replacing a nucleus pulposus in an intervertebral disc,comprising the steps of:

-   -   a. removing the nucleus pulposus from the intervertebral disc to        create a space,    -   b. inserting into the space a balloon having an inlet port and        an outlet port,    -   c. conducting a first discrete amount of a fluid comprising a        curable nucleus replacement material through the inlet port and        into the balloon, and

conducting a second discrete amount of the fluid through the inlet portand into the balloon.

Preferably, conduction of the fluids is accomplished by i) providing afluid connection between a syringe containing the curable nucleusreplacement material and the inlet port of the balloon, and ii)actuating the syringe to inject the fluid through the inlet port andinto the balloon. In some embodiments thereof, the syringe is adapted toexpel the fluid in discrete amounts. In some embodiments, the syringehas a threaded barrel, and its plunger is threaded and has an enlargedproximal end so that mechanical advantage may be employed. In someembodiments, the syringe contains a ratchet. In some embodiments, priorto conduction of the discrete amounts of curable nucleus replacementmaterial, a fluid comprising a radiopaque material is conducted throughthe inlet port and into the balloon, and thereafter the balloon isfluoroscopically assessed.

Therefore, in accordance with the present invention, there is provided adevice for replacing a nucleus pulposus in an intervertebral disc,comprising:

-   -   a) a catheter having an inlet tube having a proximal end opening        and a distal end opening and an outlet tube,    -   b) a balloon having an inlet port and an outlet port, wherein        the inlet port is connected to the distal end opening of the        inlet tube and the outlet port is connected to the outlet tube,        and    -   c) an injection device containing a curable nucleus replacement        material, the injection device connected to the proximal end        opening of the inlet tube.

Also in accordance with the present invention, there is provided adevice for replacing a nucleus pulposus in an intervertebral disc,comprising;

-   -   a) an inlet catheter having a proximal end opening and a distal        end opening,    -   b) an outlet catheter,    -   c) a balloon having an inlet port and an outlet port, wherein        the inlet port is connected to the distal end opening of the        inlet catheter and the outlet port is connected to the outlet        catheter, and    -   d) an injection device containing a curable nucleus replacement        material, the injection device connected to the proximal end        opening of the inlet catheter.

In another embodiment of the present invention, two separate, adjacentballoons are employed. A first trial balloon is filled to occupy thedisc space, and the appropriate volume is determined thereby. Followingthis measurement step, this first trial balloon is deflated as thesecond implant balloon is filled with nucleus replacement material. Thissecond filling is conducted in a manner that will substantially maintainthe volume obtained during the filling of the first balloon.

Therefore, in accordance with the present invention, there is provided amethod of replacing a nucleus pulposus in an intervertebral disc,comprising the steps of:

-   -   a) removing the nucleus pulposus from the intervertebral disc to        create a space,    -   b) inserting into the space a first balloon having an inlet port        and an outlet port and a second balloon having an inlet port and        an outlet port,    -   c) conducting a first fluid comprising a radiopaque agent        through the inlet port and into the first balloon to        substantially fill the space, and    -   d) conducting a second fluid comprising a nucleus replacement        material into the second balloon to displace the first fluid        through the outlet port of the first balloon.

Preferably, conduction of the curable nucleus replacement material intothe second implant balloon is carried out at substantially the samepressure produced in the first trial balloon by conduction of the fluidcomprising the radiopaque material.

Preferably, the amount of the radiopaque fluid conducted into the firsttrial balloon is measured prior to conducting the fluid comprising thecurable nucleus replacement material into the second trial balloon.Alternatively, the first trial balloon injected with the radiopaquematerial is fluoroscopically assessed.

After the fluid comprising the curable nucleus replacement materialfills the second implant balloon, it is allowed to cure. Then, the inletand outlet ports are removed from the balloons.

DESCRIPTION OF THE FIGURES

FIG. 1 discloses a cross-section of a damaged intervertebral disc.

FIG. 2 discloses a cross-section of an intervertebral disc having amajority of the nucleus pulposus removed.

FIG. 3 discloses a cannula inserted into the disc of FIG. 2 through ahole in the annulus fibrosus.

FIG. 4 discloses a single balloon inserted into the disc of FIG. 3through the cannula.

FIG. 5 discloses filling the balloon of FIG. 4 with a radiopaque agent.

FIG. 6 discloses displacing the radiopaque agent of FIG. 5 with anucleus replacement material.

FIG. 7 discloses the balloon of FIG. 6 completely filled with nucleusreplacement material.

FIG. 8 discloses the balloon of FIG. 7 having its ports removed.

FIG. 9 discloses a dual balloon device inserted into the disc of FIG. 3through the cannula.

FIG. 10 discloses filling the trial balloon of FIG. 9 with a radiopaqueagent.

FIG. 11 discloses the implant balloon of FIG. 10 filled with nucleusreplacement material and a deflated trial balloon.

FIG. 12 discloses a side view of a functional spinal unit, wherein thedisc space therein has a balloon of the present invention havingmultiple stacked (empty) chambers.

FIG. 13 discloses the balloon of FIG. 12 filled to create the lordosis,wherein the chambers increase in length at higher locations in the discspace.

FIG. 14 discloses a side view of a functional spinal unit, wherein thedisc space therein has a balloon of the present invention havingmultiple stacked (filled) chambers to create the lordosis, wherein thechambers increase in length at higher locations in the disc space.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention, a “discectomy” involves theremoval of at least a portion of the nucleus pulposus of a degenerateddisc. Often, the entire nucleus pulposus is removed. Frequently, a smallamount of tissue from the annulus fibrosus portion of the intervertebraldisc is removed as well, thereby leaving a central disc space surroundedby the remaining portion of the annulus fibrosus.

FIG. 1 discloses a cross section of a damaged intervertebral disc.

In performing a preferred method of the present invention, first, adiscectomy is performed by creating a hole in the annulus fibrosus ofthe degenerating disc, inserting a tissue removal instrument (such asrongeurs) into the hole, and removing nucleus pulposus tissue from thecentral portion of the disc. The resulting structure is that shown inFIG. 2, wherein a portion of the nucleus pulposus is removed. Nowreferring to FIG. 3, a cannula 1 is inserted into the hole in theannulus fibrosus.

In some embodiments, the device comprises a single balloon.

Now referring to FIG. 4, the single balloon device of the presentinvention is inserted into the cannula. The device comprises a balloon 3having an inlet port 5 and a outlet port 7. Now referring to FIG. 5,trial material is flowed through the inlet port and into the balloon tofill the balloon with trial material. In one embodiment, the trialmaterial is saline comprising a radiopaque agent. Now referring to FIG.6, once the trial material has been used to assess the disc space, theoutlet port is opened and nucleus replacement material is flowed intothe balloon, thereby displacing the trial material. In FIG.6, thenucleus replacement material has displaced about half od the trialmaterial from the balloon. Now referring to FIG. 7, the filling of theballoon with nucleus replacement material continues until the balloon iscompletely filled with nucleus replacement material. Now referring toFIG. 8, once the balloon is completely filled with nucleus replacementmaterial, the outlet port and the inlet port are removed.

In some embodiments, the device comprises two balloons.

Now referring to FIG. 9, next, the device comprising both a trialballoon and an implant balloon is inserted directly into the disccavity, preferably by being delivered through a minimally invasivecannula. The inlet and outlet ports for each balloon are shown exitingthe cannula.

Now referring to FIG. 10, next, the trial balloon is then inflated toconform to the cleared disc space cavity.

Next, the volume of the intradiscal cavity is obtained by monitoringeither the volume of material injected into the balloon, or the pressurein comparison to known balloon expansion values. Intra-operative imagingis then performed to determine the coronal, saggital, and axialplacement of the device, as well as the size, angle and geometry of thecleared disc space. The intra-operative imaging may include the use of aC-arm, cineradiography or image guided surgery.

Next, the surgeon makes an intraoperative determination as to whether anadequate intradiscal cavity has been created. If the surgeon determinesthat the intradiscal cavity is insufficient (for example, the disc spaceis located to the left of center), the surgeon deflates and removes thedevice, performs additional discectomy, and then again ascertains thedisc space clearance with the trial balloon portion of the device.

Based upon the surgeon's assessment of the amount, size and shape of thedisc space cleared, the surgeon can select the appropriate disctreatment procedure, including the injection or insertion of nuclear andannular augmentation materials, disc replacement devices or fusiondevices.

Now referring to FIG. 11, if the surgeon decides to replace the nucleuswith a nucleus replacement material, the surgeon then fills the implantballoon with a curable nucleus replacement material while deflating thetrial balloon. The surgeon then allows the curable material to cure,thereby producing the desired implant.

Therefore, in preferred embodiments, there is provided a method forreplacing a nucleus pulposus, comprising the steps of:

-   -   a) performing a discectomy to create a disc space;    -   b) inserting a device comprising a deflated trial balloon and a        deflated implant balloon into the disc space;    -   c) expanding the deflated trial balloon,    -   d) assessing the disc space via the inflated trial balloon,    -   e) deflating the trial balloon while inflating the implant        balloon with a curable nucleus replacement material; and    -   f) curing the curable nucleus replacement material.

The above steps will now be discussed in greater detail.

In a preferred embodiment of the present invention, at least a portionof each of the nucleus pulposus and the annulus fibrosus is removed witha disc removal instrument to create a disc space DS. Suitable discremoval instruments include rongeurs, trephines, burrs and curettes. Insome embodiments, the method includes removing at least a portion of thenucleus pulposus, wherein the removal step includes creating a vacuum orproviding irrigation. In some embodiments, the irrigation is provided bythe same cannulated instrument that delivers and expands the balloon. Insome embodiments, the method includes removing at least a portion of thenucleus pulposus, wherein the removal step is achieved via chemicaldissolution of the nucleus pulposus.

Next, the device comprising the trial balloon and implant balloon isinserted into the disc space in a deflated form. The device comprises:

-   -   a) a trial balloon having a lumen and comprising a first        expandable material, and    -   b) a trial tube having a proximal end portion, a distal end        portion, and a throughbore (not shown),    -   c) an implant balloon having a lumen and comprising a second        expandable material, and    -   d) an implant tube having a proximal end portion, a distal end        portion, and a throughbore (not shown),        wherein the trial balloon lumen is connected to the distal end        portion of the trial tube and is in fluid communication with its        throughbore, and        wherein the implant balloon lumen is connected to the distal end        portion of the implant tube and is in fluid communication with        its throughbore.

In some embodiments, and as shown, the device is inserted into the discspace through a cannula. So as to avoid further damage to the annulus,preferably, the cannula is sized to be smaller than the annular openingcreated in the disc. In other embodiments, the device is insertedwithout the aid of a cannula.

The balloons can be delivered to the disc space by any suitable means,e.g., in deflated form retained within or upon the end of a rigid orsemi-rigid rod or tube.

In some embodiments, the balloons may also be inserted through a holecreated in an endplate of an adjacent vertebra above or below the targetdisc. The balloons may also be inserted into the disc space via aposterior, anterior or anterolateral approach.

Once positioned within the disc space, either centrally within theannular shell or at the edge of the annular rim, a suitable gas (e.g.,nitrogen or carbon dioxide), liquid or other flowable expansion mediumcan be delivered through the tube in order to inflate the trial balloonin situ in a substantially radial, axial and/or longitudinal direction.In some embodiments, beads or other solid media are selected to be theexpansion medium and are simply packed into the balloon through thetube.

Next, the trial balloon is expanded while in the disc space. Preferably,the trial balloon is expanded with radio-opaque media (not shown), suchas a radio-opaque gas or liquid, or with radio-opaque beads. Onceexpanded, the trial balloon may be imaged intra-operatively in order todetermine the size, shape and location of the disc space. The trialballoon is only partially expanded in the disc space. Preferably, thetrial balloon is expanded to completely fill the disc space.

Next, the surgeon makes an intraoperative determination as to whether anadequate intradiscal cavity has been created. In some embodiments, thisdetermination is made by either pressure assessment, fluoroscopicassessment or volumetric assessment. If the surgeon determines that theintradiscal cavity is insufficient (for example, the disc space islocated to the left of center), the surgeon deflates and removes thedevice, performs additional discectomy, and then again ascertains thedisc space clearance with the trial balloon portion of the device.

Based upon the surgeon's assessment of the amount, size and shape of thedisc space cleared, the surgeon can select the appropriate disctreatment procedure, including the injection or insertion of nuclear andannular augmentation materials, disc replacement devices or fusiondevices.

If, through the assessment, the surgeon has decided that sufficient discspace has been cleared, the surgeon then opens the exit port of thetrial balloon and deflates the trial balloon (by, for example, providingsuction through the exit port) while simultaneously filling the implantballoon with curable implant material. The simultaneously deflation ofthe trial balloon and inflation of the implant balloon is carried outunder constant pressure or volume, so that when the trial balloon isdeflated the implant balloon occupies substantially the same space asthe trial balloon had occupied. Preferably, the simultaneousdeflation/inflation of the balloons is carried out in a manner so as tomaintain the disc height spacing created by the trial balloon. In somepreferred embodiments, the implant balloon is filled through theinjection of a plurality of discrete amounts of curable implantmaterial. The injection of a plurality of discrete amounts of curableimplant material allows the surgeon to accurately fill the balloon in ahighly controlled manner. Once the implant balloon is completely filled,the cannulae connected with the balloons are removed. Optionally, thetrial balloon may be removed as well. The material in the implantballoon is then allowed to cure.

Therefore, in accordance with the present invention, there is provided adevice for replacing a nucleus pulposus in an intervertebral disc,comprising;

-   -   a) a first catheter having a first inlet tube having a proximal        end opening and a distal end opening and a first outlet tube,    -   b) a first balloon having an inlet port and an outlet port,        wherein the inlet port is connected to the distal end opening of        the first inlet tube and the outlet port is connected to the        first outlet tube, and    -   c) a first injection device containing a flowable radiopaque        material, the first injection device connected to the proximal        end opening of the inlet catheter.    -   d) a second catheter having a second inlet tube having a        proximal end opening and a distal end opening and a second        outlet tube,    -   e) a second balloon having an inlet port and an outlet port,        wherein the inlet port is connected to the distal end opening of        the second inlet tube, and    -   f) a second injection device containing a curable nucleus        replacement material, the injection device connected to the        proximal end opening of the second inlet tube.

Also in accordance with the present invention, there is provided adevice for device for replacing a nucleus pulposus in an intervertebraldisc, comprising;

-   -   a) a first inlet catheter having a proximal end opening and a        distal end opening,    -   b) a first outlet catheter,    -   c) a first balloon having an inlet port and an outlet port,        wherein the inlet port is connected to the distal end opening of        the first inlet catheter and the outlet port is connected to the        first outlet catheter, and    -   d) a first injection device containing a flowable radiopaque        material, the first injection device connected to the proximal        end opening of the inlet catheter.    -   e) a second inlet catheter having a proximal end opening and a        distal end opening,    -   f) a second balloon having an inlet port and an outlet port,        wherein the inlet port is connected to the distal end opening of        the second inlet catheter, and    -   g) a second injection device containing a curable nucleus        replacement material, the injection device connected to the        proximal end opening of the second inlet catheter.

It may sometimes occur that the surgeon expands the trial balloon anddecides that additional height is needed. Therefore, in some embodiment,there is provided a device comprising multiple, vertically arrangedballoons. When such a balloon is provided, the surgeon fills the baseballoon, and then has the option of filling the superior balloon inorder to create more height in the trial or implant balloon. Theprovision of multiple balloons in the same device avoids the need toreplace the undersized ballon and associated catheter with larger oneswhen the need for additional fill has been determined. In someembodiments, the plurality of balloons may take the form of stackedbaffles. In some embodiments, the different balloons within the samedisc are provided with different pressures or different compressiblematerials in order to obtain different properties for different balloonswithin the same disc. For example, in one embodiments, some but not allof the balloons may be provided with particles that resist shear anddampen axial forces. In some embodiments, the balloons that are closerto the endplates are stiffer than those further away from the endplates.In some embodiments thereof, the stacking could be produced via multiplechambers of the same balloon.

In the lumbar region of the spine, the natural positioning of thevertebral endplates is such that the intervening disc has a wedged shapeand provides a lordotic curvature to the spine. Therefore, it would bedesirable for the implant balloon of the present invention to expandinto a wedged shape that mimics the lordotic curvature of the spine. Inother embodiments, the lordotic curvature is attained by implanting atleast two balloons in a vertically arranged manner whereby the shape andspatial arrangement of the two balloons form a wedged shape and impart alordotic curvature to the spine. In some embodiments thereof, thelordosis could be produced via multiple chambers of the same balloon.Now referring to FIG. 12, there is provided a balloon of the presentinvention having multiple stacked (empty) chambers which has beeninserted into the disc space. Now referring to FIG. 13, there isprovided a balloon of the present invention having multiple stackedchambers which have been filled to create the desired lordosis. In thisparticular embodiment, the chambers increase in length at higherlocations in the disc space. Now referring to FIG. 14, there is provideda balloon of the present invention having multiple stacked chamberswhich have been filled to create the desired lordosis. In thisparticular embodiment, the chambers decrease in length at higherlocations in the disc space.

In some embodiments, ultrasound is used to assess the shape of theexpanded balloon. In these embodiments, the expandable device (such as aballoon) is expanded within the disc space and ultrasound is then usedto assess its shape. In some embodiments, the surgeon carries out anultrasound-based assessment of the balloon after injecting theradiopaque material and before injecting the curable nucleus replacementmaterial. The ultrasound assessment may be carried out with or withoutthe balloon in place. If there is an intact annulus, the balloon may beused to pressurize the voided space and ultrasound may then be used toassess that pressurized space.

Each expandable device or membrane of the present invention (such as aballoon) has at least one lumen, an inside surface, and an outersurface. Also, each balloon has an upper side, a lower side, an anteriorside and a posterior side. The trial balloon is typically expanded bypassing an expansion medium, such as a fluid or beads, through the lumento fill the balloon. The implant balloon is typically expanded byfilling it with a curable implant material.

Suitable materials for preparing balloons of the present invention mayinclude those that are presently used for such purposes as balloonangioplasty. Suitable materials provide an optimal combination of suchproperties as compliance, biostability and biocompatability, andmechanical characteristics such as elasticity and strength. Balloons canbe provided in any suitable form, including those having a plurality oflayers and those having a plurality of compartments when expanded. Auseful device will include the balloons, together with a deliverycatheter (optionally having a plurality of lumens extendinglongitudinally therewith), and fluid or gas pressure means.

The balloons are typically made of an expandable material such as aplastic or elastomeric material. Examples thereof include silicone,polyurethane, polyethylene terephthalate, polycarbonate, thermoplasticelastomers and copolymers such as ether-ketone polymers such aspoly(etheretherketone). Such polymeric materials can be used in eitherunsupported form, or in supported form, e.g., by the integration offibers therein. In addition, the balloons may be made out of any of awide variety of woven or nonwoven fibers, fabrics, metal mesh such aswoven or braided wires, and carbon. Biocompatible fabrics or sheetmaterial such as ePTFE and Dacron™ may also be used.

In a particularly preferred embodiment, the balloons comprise a materialselected from the group consisting of polyolefin copolymers,polyethylene, polycarbonate, polyethylene terephthalate, ether-ketonepolymers, woven fibers, nonwoven fibers, fabrics and metal mesh.

A radio-opaque material may be mixed with the expandable material toprovide a radio-opaque balloon having imaging capability. Theradio-opaque material may be provided in the form of a filler,particles, wires or shapes. Suitable radio-opaque materials includebarium, barium sulfate, calcium or metallic materials.

The balloons can include markers commonly used in image guided surgeryto allow three dimensional reconstruction of the cleared disc space ascompared to a preoperatively obtained reconstructed MRI and/or CT. Themarkers are preferably located upon the outside surface of the balloon.The markers may have spatially varying sizes, shapes or concentrations.

Because volume controlled systems are preferred embodiments of thepresent invention, in some embodiments, the expandable material of theballoon can be a non-compliant material that expands to a predeterminedsize. In some preferred embodiments, the distraction of the disc spaceis accomplished by such an inflatable, rigid (non-compliant) balloon.The non-compliant balloon can be delivered in deflated form to theinterior of the annulus and thereafter inflated in order to distract thedisc space and provide a spaced region for the delivery of the implantmaterial. The balloon is preferably of sufficient strength and ofsuitable dimensions to distract the space to a desired extent and tomaintain the space in distracted position for a sufficient period oftime.

In one embodiment, at least the implant balloon has a wedged shape sothat the height of the anterior portion of the expanded device isgreater than the height of the posterior portion of the expanded device.This allows the surgeon to restore lordosis when the intervertebralimplant is used in either the lumbar or cervical regions of the spine.Preferably, the wedged shape produces an angle of between 5 and 20degrees, more preferably between 5 and 15 degrees.

In preferred embodiments, the height of the medial portion of at leastthe implant balloon is greater than the height of either lateral portionof the implant balloon. This geometry more closely mimics the naturaldoming of the disc space.

In some embodiments, the device can comprise at least one balloon ofsemicircular, circular, cylindrical, bilateral, or a generally crescent(or banana-like) shape. Upon inflation, each balloon can have afootprint that substantially corresponds to (but is smaller than) a rimof a vertebral endplate, wherein the anterior area height is greaterthan said posterior area height. More preferably, upon expansion, atleast a portion of the balloon has a generally cylindrical shape therebydefining an axial dimension and a radial dimension.

In some preferred embodiments, the balloons may also be used to distractthe cleared disc space. When inflated, a non-compliant balloon mayprovide rigid walls (e.g., when they are fiber-supported orbellows-supported) that are sufficiently strong to distract the space.An inflatable device providing sufficient strength and dimensions fordistraction can be prepared using conventional materials. In oneembodiment, the uninflated balloon can be delivered to the center of theannular shell, and thereafter inflated to expand the annular shell andin turn, distract the space. Preferably, the expansion medium isinjected in an amount sufficient to distract the space.

As used herein, the word “distraction” will refer to the separation ofthe intervertebral joint surfaces to a desired extent, without ruptureof their binding ligaments. Distraction can be accomplished by anysuitable means including, for example, hydrostatic means. In oneembodiment, the trial balloon is used as a distraction device. By theuse of distraction, the disc space can be sufficiently re-established toachieve any desired final dimensions and position. Optionally, andpreferably, the means used to accomplish distraction also serves thepurpose of forming one or more barriers (e.g., balloons) for theflowable expansion media. If distraction is desired, then the disc spacecan be distracted prior to and/or during either a discectomy itselfand/or delivery of a flowable expansion medium.

A constricted disc space is generally on the order of 3 to 4 mm inheight. Suitable distraction means are capable of providing on the orderof about 3 atmospheres to about 4 atmospheres, (or on the order of about40 psi to about 60 psi) of force in order to distract that disc space toon the order of 8 to 12 mm in height. Preferably, when used fordistraction, the balloon of the present invention is designed towithstand at least 1 MPa of pressure, more preferably at least 2 MPa,more preferably at least 3 MPa.

Distraction may occur via a multitude of steps or iterations, therebyallowing the soft tissue to relax, thus reducing the risk of soft tissuedamage.

Preferably, the expansion media of the in situ formed device can bedelivered percutaneously (e.g., through a cannula having a diameter ofno more than 6 mm, preferably no more than 2 mm). However, the expansionmedia of the in-situ formed device can also be delivered in cannulae ofmuch larger dimension (such as up to 18 mm, or through a Craig needle).More preferably, the expansion media of the in-situ formed device isdelivered into the disc space in the form of an injectable fluid.

It has been reported in the literature that balloons inserted into thedisc space may be subject to retropulsion. Therefore, in someembodiments of the present invention, and particularly those thatinclude distraction, upon expansion, the inflatable implant balloonforms an upper surface having a first plurality of teeth projectingoutwards from the upper surface. Upon expansion of the device, theseteeth will project in the direction of the upper endplate and, uponcomplete expansion of the device, will engage the endplate to from asecure interlock with the endplate and resist retropulsion.

In some embodiments, the implant balloon can be coated with an adhesivesuch as a protein activated sealant, or a sealant that becomes adhesivewhen wetted or activated.

Preferably, the teeth are made of a stiff non-resorbable material, suchas polyetheretherketone (PEEK). Preferably, the teeth have a height ofbetween 0.5 mm and 1.5 mm, and have a triangular cross-section.

In some embodiments of the present invention, upon expansion, theinflatable implant balloon forms an upper surface formed of a materialhaving a high coefficient of friction. Upon expansion of the device, thehigh coefficient of friction of the upper and lower surfaces will causea drag upon any movement of the upper surface and therefore keep thedevice in place and resist retropulsion.

Preferably, the high friction upper and lower surfaces of the implantballoon device are made from a material selected from a group consistingof polyether block copolymer (PEBAX), ABS (acrylonitrile butadienestyrene); ANS (acrylonitrile styrene); Delrin®; PVC (polyvinylchloride); PEN (polyethylene napthalate); PBT (polybutyleneterephthalate); polycarbonate; PEI (polyetherimide); PES (polyethersulfone); PET (polyethylene terephthalate); PETG (polyethyleneterephthalate glycol), high and medium melt temperature: polyamides,aromatic polyamides, polyethers, polyesters, Hytrell®,polymethylmethacrylate, polyurethanes: copolymers, EVA (ethylene vinylacetate) or ethylene vinyl alcohol; low, linear low, medium and highdensity polyethylenes, latex rubbers, FEP, TFE, PFA, polypropylenes,polyolefins; polysiloxanes, liquid crystal polymers, inomers, Surlins,silicone rubbers, SAN (styrene acrylonitrile), nylons: 6, 6/6, 6/66,6/9, 6/10, 6/12, 11, all PEBAXs 12; polyether block amides; andthermoplastic elastomers.

Balloons of the present invention can be made using materials andmanufacturing techniques used for balloon angioplasty devices. U.S. Pat.No. 5,807,327 (“Green”) discloses balloons that may be used in thepresent invention. The materials disclosed by Green for the formation ofthe balloon include tough non-compliant layer materials (col. 8, lines18-36 of Green) and high coefficient of friction layer materials (col.8, lines 42-54 of Green).

Generally, the balloon is deliverable through a cannula having an insidediameter of between 3 mm and 18 mm, preferably between 4 mm and 12 mm,more preferably between 5 mm and 10 mm.

In some preferred embodiments, a cannula having an inner diameter of nomore than 6 mm, is inserted into the disc space.

In some embodiments in which the surgeon desires to minimize the size ofthe incision, the balloon is preferably deliverable through a cannulahaving an inside diameter of between 0.5 mm and 6 mm, preferably between1 mm and 4 mm, more preferably between 2 mm and 3 mm.

In some embodiments, the present invention can be used to providegradual correction of a scoliotic disc. The degree of curvature can begradually changes over time by, for example, pumping up the balloonswith a syringe.

1. A method of replacing a nucleus pulposus in an intervertebral disc,comprising the steps of: a) removing the nucleus pulposus from theintervertebral disc to create a space, b) inserting into the space aballoon having an inlet port and an outlet port, c) conducting an amountof a first fluid comprising a radiopaque agent through the inlet portand into the balloon to produce a first pressure in the balloon, d)conducting a second fluid comprising a curable nucleus replacementmaterial through the inlet port and into the balloon to displace thefirst fluid through the outlet port,
 2. The method of claim 1 whereinstep d) is carried out at substantially the first pressure.
 3. Themethod of claim 1 wherein the amount of the first fluid conducted intothe balloon is measured prior to step d).
 4. The method of claim 1further comprising: e) curing the curable nucleus replacement material.5. The method of claim 4 wherein the inlet and outlet ports are removedfrom the balloon after step e).
 6. The method of claim 1 furthercomprising the step, between steps c) and d), of: e) fluoroscopicallyassessing the balloon.
 7. The method of claim 1 further comprising thestep, between steps c) and d), of: e) assessing the balloon withultrasound.
 8. A method of replacing a nucleus pulposus in anintervertebral disc, comprising the steps of: a) removing the nucleuspulposus from the intervertebral disc to create a space, b) insertinginto the space a balloon having an inlet port and an outlet port, c)conducting a first discrete amount of a fluid comprising a curablenucleus replacement material through the inlet port and into theballoon, and d) conducting a second discrete amount of the fluid throughthe inlet port and into the balloon.
 9. The method of claim 8 whereinconduction of the fluids is accomplished by i) providing a fluidconnection between a syringe containing the curable nucleus replacementmaterial and the inlet port of the balloon, and ii) actuating thesyringe to inject the fluid through the inlet port and into the balloon.10. The method of claim 9 wherein the syringe is adapted to expel thefluid in discrete amounts.
 11. The method of claim 9 wherein the syringehas a threaded barrel.
 12. The method of claim 8 wherein the ballooncomprises a radiopaque material.
 13. The method of claim 8 furthercomprising the step, prior to step c), of e) conducting a fluidcomprising a radiopaque material through the inlet port and into theballoon.
 14. The method of claim 8, further comprising the step, betweensteps c) and d), of: e) fluoroscopically assessing the balloon.
 15. Themethod of claim 8 further comprising the step of: e) curing the curablenucleus replacement material.
 16. A method of replacing a nucleuspulposus in an intervertebral disc, comprising the steps of: a) removingthe nucleus pulposus from the intervertebral disc to create a space, b)inserting into the space a first balloon having an inlet port and anoutlet port and a second balloon having an inlet port and an outletport, c) conducting a first fluid comprising a radiopaque agent throughthe inlet port and into the first balloon to substantially fill thespace, and d) conducting a second fluid comprising a nucleus replacementmaterial into the second balloon to displace the first fluid through theoutlet port of the first balloon.
 17. The method of claim 16 whereinstep d) is carried out at substantially the first pressure.
 18. Themethod of claim 16 wherein the amount of the first fluid conducted intothe balloon is measured prior to step d).
 19. The method of claim 16further comprising: e) curing the curable nucleus replacement material.20. The method of claim 19 wherein the inlet and outlet ports areremoved from the second balloon after step e).
 21. The method of claim16 further comprising the step, between steps c) and d), of: e)fluoroscopically assessing the balloon.
 22. The method of claim 16wherein the first balloon comprises a radiopaque material.
 23. Themethod of claim 16 wherein step d) is carried out at substantiallyconstant volume
 24. A device for replacing a nucleus pulposus in anintervertebral disc, comprising; a) a catheter having an inlet tubehaving a proximal end opening and a distal end opening and an outlettube, b) a balloon having an inlet port and an outlet port, wherein theinlet port is connected to the distal end opening of the inlet tube andthe outlet port is connected to the outlet tube, and c) an injectiondevice containing a curable nucleus replacement material, the injectiondevice connected to the proximal end opening of the inlet tube.
 25. Thedevice of claim 24 wherein the injection device is adapted to ejectcontrolled, discrete amounts of the curable nucleus replacementmaterial.
 26. A device for replacing a nucleus pulposus in anintervertebral disc, comprising; a) an inlet catheter having a proximalend opening and a distal end opening, b) an outlet catheter, c) aballoon having an inlet port and an outlet port, wherein the inlet portis connected to the distal end opening of the inlet catheter and theoutlet port is connected to the outlet catheter, and d) an injectiondevice containing a curable nucleus replacement material, the injectiondevice connected to the proximal end opening of the inlet catheter. 27.The device of claim 26 wherein the injection device is adapted to ejectcontrolled, discrete amounts of the curable nucleus replacementmaterial.
 28. The device of claim 27 wherein the injection device is asyringe.
 29. The device of claim 28 wherein the syringe has a threadedbarrel.
 30. The device of claim 29 wherein the syringe contains aplunger having an enlarged proximal end to provide mechanical advantage.31. The device of claim 30 wherein the syringe contains a threadedplunger.
 32. The device of claim 30 wherein the syringe contains aratchet.
 33. A device for replacing a nucleus pulposus in anintervertebral disc, comprising; a) a first catheter having a firstinlet tube having a proximal end opening and a distal end opening and afirst outlet tube, b) a first balloon having an inlet port and an outletport, wherein the inlet port is connected to the distal end opening ofthe first inlet tube and the outlet port is connected to the firstoutlet tube, and c) a first injection device containing a flowableradiopaque material, the first injection device connected to theproximal end opening of the inlet catheter. d) a second catheter havinga second inlet tube having a proximal end opening and a distal endopening and a second outlet tube, e) a second balloon having an inletport and an outlet port, wherein the inlet port is connected to thedistal end opening of the second inlet tube, and f) a second injectiondevice containing a curable nucleus replacement material, the injectiondevice connected to the proximal end opening of the second inlet tube.34. A device for replacing a nucleus pulposus in an intervertebral disc,comprising; a) a first inlet catheter having a proximal end opening anda distal end opening, b) a first outlet catheter, c) a first balloonhaving an inlet port and an outlet port, wherein the inlet port isconnected to the distal end opening of the first inlet catheter and theoutlet port is connected to the first outlet catheter, and d) a firstinjection device containing a flowable radiopaque material, the firstinjection device connected to the proximal end opening of the inletcatheter. e) a second inlet catheter having a proximal end opening and adistal end opening, f) a second balloon having an inlet port and anoutlet port, wherein the inlet port is connected to the distal endopening of the second inlet catheter, and g) a second injection devicecontaining a curable nucleus replacement material, the injection deviceconnected to the proximal end opening of the second inlet catheter.